This application is related to Japanese Patent Application No. 2000-33571 filed on Feb. 10, 2000, whose priority is claimed under 35 USC xc2xa7 119, the disclosure of which is incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to an optical device, more particularly, an optical device comprised of lens plates with lens arrays formed on their faces.
2. Description of Related Art
Optical devices comprised of lens plates with lens arrays on their faces have been used in display devices and scanners to form captured images. The lens array is a set of cylindrical lenses arranged adjacently in a certain direction, for example. In the lens array, cross talk of light beams into adjacent lenses is a cause of deterioration in image-forming characteristics because it induces generation of ghosts.
For preventing this cross talk, several means have been developed so far. For example, a light-shielding pattern is formed by applying a light-shielding material to joints between lenses (lens joints) or light-shielding members are provided at lens joints.
FIG. 14 shows a sectional view of a lens plate 101 of a conventional optical device, in which a light-shielding pattern 105 is formed using a black paint to cover lens joints 106 of a cylindrical lens array 104 to prevent the cross talk to adjacent lenses. Out of light beams emitted from a light source 102, those 103 incident on the lenses of the cylindrical lens array 104 pass through the lenses without being blocked, while those incident on the light-shielding pattern 105 are blocked by the light-shielding pattern and do not pass outward (upward in the figure) from the lens plate 101.
FIG. 15 shows a sectional view of another conventional optical device, in which light-shielding members 107 absorbing incident light beams are provided between two lens plates 101 having cylindrical lens arrays 104 on their surfaces to prevent the cross talk to adjacent lenses.
These conventional optical devices cut off only the light beams directly incident on the light-shielding pattern 105 or the light-shielding members 107.
Also, inventions relating to constructions of lens arrays having grooves for preventing the cross talk are disclosed in Japanese Unexamined Patent Publications Nos. SHO 63(1988)-225218 and HEI 11(1999)-109283.
However, to cover the lens joints in the lens array with the light-shielding pattern or members can only cut off the light beams directly incident on the light-shielding pattern or members which are part of the light beams that cause the cross talk in adjacent lenses. In a lens array formed on a relatively thick lens plate with respect to an array pitch of lenses, in particular, light beams passing through the lens plate cause a plenty of cross talk in adjacent lenses. In order to prevent that, it is necessary to increase the width of the light-shielding pattern or members at the lens joints.
An increased width of the light-shielding pattern or members at the lens joints, however, involves a reduction in an effective area of the lenses. Therefore, there is a problem in that these optical devices are dark optical systems with low efficiency in use of light, although they can prevent the occurrence of the cross talk.
In addition, if the light-shielding pattern or members are disposed out of alignment with the lens joints, the cross talk cannot be prevented at all.
The present invention provides an optical device comprising a plurality of lens plates spaced at specific intervals, at least one of which is provided with a lens array on at least one of its front and rear faces, the lens array being composed of a plurality of closely arranged lenses of a specific configuration, wherein the lens array has at least one groove having a V-shaped cross-sectional configuration at a joint of adjacent lenses in at least one part of the lens array. With this construction, it is possible to reduce the cross talk by light incident from adjacent lenses and maintain good image-forming characteristics.
These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.